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Ming J.,Hanyang University | Ming H.,Soochow University of China | Yang W.,Fifth Research Institute of MIIT East China | Kwak W.-J.,Hanyang University | And 3 more authors.
RSC Advances | Year: 2015

A type of porous carbon-Fe3O4 (e.g., PC-Fe3O4) composite with an industrially scalable production was introduced in the sodium ion battery application for the first time. The PC-Fe3O4 composite, consisting of highly dispersed Fe3O4 nanocrystals within the porous carbon with a relatively low weight percent of 45.5 wt%, could efficiently demonstrate high capacities of 225, 168, 127, 103, 98 and 90 mA h g-1 under the current densities of 50, 100, 200, 300, 400 and 500 mA g-1 with a good stability over 400 cycles. The utilization co-efficient of Fe3O4 nanocrystals was proven to be much higher than most of the Fe3O4 nanoparticles reported recently via the study of the capacity contribution of carbon originally. In addition, the robustness of electrode during the charge-discharge was well characterized by ex situ XRD and emission scanning electron microscopy (SEM). More importantly, a new concept of an elemental iron-based sodium ion battery of PC-Fe3O4/Na2FeP2O7 is presented. This is the first example to introduce an element-rich configuration in the sodium ion battery from the viewpoint of sustainability. The full battery demonstrated a superior capacity of 93 mA h g-1, high capacity retention of 93.3% over 100 cycles and work voltage around 2.28 V with the energy density of 203 W h kg-1. Such configuration of an iron-based sodium battery would be highly promising and sustainable owing to its low cost and high stability in grid storage. © The Royal Society of Chemistry 2015.

Ming H.,Hanyang University | Ming H.,Soochow University of China | Ming J.,Hanyang University | Kwak W.-J.,Hanyang University | And 4 more authors.
Electrochimica Acta | Year: 2015

A new fluorine-doped porous carbon-decorated Fe3O4-FeF2 composite, referred to as Fe3O4-FeF2@CFx, was prepared for the first time. The formation mechanism is discussed, and a new concept of introducing double layers of FeF2 and CFx into the oxide-based anode is presented for lithium ion batteries. Varying the amount of fluorine precursor, derivatives of Fe3O4@CFx and FeF2@CFx were further obtained, allowing an original analysis of their electrochemical behaviors. As-prepared Fe3O4-FeF2@CFx can deliver a high capacity of 718 mAh g-1 at 50 mA g-1. Under a hash rate of 1600 mAg-1, the capacity of Fe3O4-FeF2@CFx (around 338 mAh g-1) is higher than that (200 mAh g-1) of FeF2@CFx. Further, its capacity retention of 97% over 100 cycles is much better than the 59.4% observed for Fe3O4@CFx. The positive effect of the CFx layer on the electronic conductivity and ionic diffusion ability was confirmed. The role of FeF2 in the stabilization of the structure of CFx and Fe3O4 is also discussed. Further, a new battery composed of Fe3O4-FeF2@CFx/LiNi0.5Mn1.5O4 with a robust rate capability was assembled and delivered a reversible capacity of 565 mAh g-1 (vs. anode) at 100 mA g-1 with a high potential of 3.3 V and a capacity retention of 81.5% over 50 cycles. © 2015 Elsevier Ltd. All rights reserved.

Ming H.,Soochow University of China | Kumar P.,King Abdullah University of Science and Technology | Yang W.,Fifth Research Institute of MIIT East China | Fu Y.,Soochow University of China | And 5 more authors.
ACS Sustainable Chemistry and Engineering | Year: 2015

A green hydrothermal strategy starting from the Ti powders was developed to synthesis a new kind of well dispersed anatase TiO2 nanosheets (TNSTs) with dominant (001) facets, successfully avoiding using the HF by choosing the safe substitutes of LiF powder. In contrast to traditional approaches targeting TiO2 with dominant crystal facets, the strategy presented herein is more convenient, environment friendly and available for industrial production. As a unique structured anode applied in lithium ion battery, the TNSTs could exhibit an extremely high capacity around 215 mAh g-1 at the current density of 100 mA g-1 and preserved capacity over 140 mAh g-1 enduring 200 cycles at 400 mA g-1. As a further step toward commercialization, a model of lithiating TiO2 was built for the first time and analyzed by the electrochemical characterizations, and full batteries employing lithiated TNSTs as carbon-free anode versus spinel LiNixMn2-xO4 (x = 0, 0.5) cathode were configured. The full batteries of TNSTs/LiMn2O4 and TNSTs/LiNi0.5Mn1.5O4 have the sustainable advantage of cost-effective and cobalt-free characteristics, and particularly they demonstrated high energy densities of 497 and 580 Wh kganode -1 (i.e., 276 and 341 Wh kgcathode -1) with stable capacity retentions of 95% and 99% respectively over 100 cycles. Besides the intriguing performance in batteries, the versatile synthetic strategy and unique characteristics of TNSTs may promise other attracting applications in the fields of photoreaction, electro-catalyst, electrochemistry, interfacial adsorption photovoltaic devices etc. © 2015 American Chemical Society.

Bu L.,Hunan Normal University | Yang W.,Fifth Research Institute of MIIT East China | Ming H.,Soochow University of China
RSC Advances | Year: 2015

Uniform rutile TiO2 single crystal nanorods (TNRs) enclosed by a high amount of active (002) facets were synthesized for the first time by treating anatase TiO2 with concentrated HNO3 under hydrothermal conditions. It was found that these TNRs exhibited considerably enhanced photocatalytic activity compared to bulk rutile TiO2 owing to the highly exposed active (002) facets. In addition, gold nanoparticles with diameters of 1-5 nm were successfully deposited on the TNRs (Au/TNRs) using a simple photocatalytic reduction of HAuCl4 by the TNRs in the presence of 2-propanol. The plasmon-induced photocatalytic chemistry of the Au/TNRs under ultraviolet and visible light was investigated. The photocatalytic ability of TNRs was clearly enhanced under ultraviolet light with the decoration of Au nanoparticles. In particular, in our experimental conditions, the Au/TNRs nanocomposite demonstrated much better photocatalytic ability under visible-light than under ultraviolet light. This phenomenon may be attributed to the intense localization of plasmonic near-fields close to the Au/TiO2 interface, which brings about enhanced optical absorption and is good for generating electron-hole pairs for photocatalysis. This journal is © The Royal Society of Chemistry 2015.

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